Method and apparatus for switching of multicast and broadcast service between multicast and unicast in a wireless communication system

ABSTRACT

A method and apparatus for switching of multicast and broadcast service between multicast and unicast in a wireless communication system is described. A CU-CP establishes a connection with a wireless device for a Multicast and/or Broadcast Service (MBS). A CU-CP receives, from the CU-UP, a first message including a retransmission information on data transmission related to the MBS. A CU-CP determines whether to perform a switch of the first transmission to a second transmission for the MBS based on the retransmission information.

BACKGROUND Technical Field

The present disclosure relates to a method and apparatus for switching of multicast and broadcast service between multicast and unicast in a wireless communication system.

Related Art

3rd generation partnership project (3GPP) long-term evolution (LTE) is a technology for enabling high-speed packet communications. Many schemes have been proposed for the LTE objective including those that aim to reduce user and provider costs, improve service quality, and expand and improve coverage and system capacity. The 3GPP LTE requires reduced cost per bit, increased service availability, flexible use of a frequency band, a simple structure, an open interface, and adequate power consumption of a terminal as an upper-level requirement.

Work has started in international telecommunication union (ITU) and 3GPP to develop requirements and specifications for new radio (NR) systems. 3GPP has to identify and develop the technology components needed for successfully standardizing the new RAT timely satisfying both the urgent market needs, and the more long-term requirements set forth by the ITU radio communication sector (ITU-R) international mobile telecommunications (IMT)-2020 process. Further, the NR should be able to use any spectrum band ranging at least up to 100 GHz that may be made available for wireless communications even in a more distant future.

The NR targets a single technical framework addressing all usage scenarios, requirements and deployment scenarios including enhanced mobile broadband (eMBB), massive machine-type-communications (mMTC), ultra-reliable and low latency communications (URLLC), etc. The NR shall be inherently forward compatible.

SUMMARY Technical Objects

In NR, Multicast and Broadcast Services (MBS) may be supported. For example, the MBS may be provided for wireless devices in RRC_CONNECTED state.

A wireless device may receive MBS via multicast transmission or unicast transmission from a network. For example, multicast transmission may be referred as a point to multipoint (PTM) transmission, and unicast transmission may be referred as point to point (PTP) transmission.

A network may need to perform dynamic change of MBS delivery between multicast transmission and unicast transmission with service continuity for a wireless device in a connected state. For example, if the service continuity for a wireless device during the change is not guaranteed, user experience may be degraded.

Therefore, studies for switching of multicast and broadcast service between multicast and unicast in a wireless communication system are needed.

Technical Solutions

In an aspect, a method performed by a Central Unit (CU)-Control Plane (CP) of a Radio Access Network (RAN) node in a wireless communication system is provided. A CU-CP establishes a connection with a wireless device for a Multicast and/or Broadcast Service (MBS). A CU-CP receives, from the CU-UP, a first message including a retransmission information on data transmission related to the MBS. A CU-CP determines whether to perform a switch of the first transmission to a second transmission for the MBS based on the retransmission information.

In another aspect, an apparatus for implementing the above method is provided.

Technical Effects

The present disclosure may have various advantageous effects.

According to some embodiments of the present disclosure, a Radio Access Network (RAN) node (for example, a base station such as an eNB or a gNB) could efficiently perform switching of multicast and broadcast service between multicast and unicast.

For example, a RAN node could efficiently determine to switch between unicast and multicast for the MBS based on radio situation of the gNB-CU-UP.

For example, a gNB-central unit (CU)-Control Plane (CP), a gNB-CU-User Plane (UP), and a gNB-distributed unit (DU) could perform the switching between unicast and multicast for the MBS efficiently.

Therefore, the RAN node could use the radio resource for multicast and/or broadcast efficiently. In addition, a wireless communication system could avoid the degradation of user experience by switching of multicast and broadcast service between multicast and unicast efficiently.

According to some embodiments of the present disclosure, a wireless communication system could provide an efficient solution for switching of multicast and broadcast service between multicast and unicast by considering radio situation of the gNB-CU-UP.

Advantageous effects which can be obtained through specific embodiments of the present disclosure are not limited to the advantageous effects listed above. For example, there may be a variety of technical effects that a person having ordinary skill in the related art can understand and/or derive from the present disclosure. Accordingly, the specific effects of the present disclosure are not limited to those explicitly described herein, but may include various effects that may be understood or derived from the technical features of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a communication system to which implementations of the present disclosure is applied.

FIG. 2 shows an example of wireless devices to which implementations of the present disclosure is applied.

FIG. 3 shows an example of a wireless device to which implementations of the present disclosure is applied.

FIG. 4 shows an example of UE to which implementations of the present disclosure is applied.

FIGS. 5 and 6 show an example of protocol stacks in a 3GPP based wireless communication system to which implementations of the present disclosure is applied.

FIG. 7 shows an example of the overall architecture of an NG-RAN to which technical features of the present disclosure can be applied.

FIG. 8 shows an interface protocol structure for F1-C to which technical features of the present disclosure can be applied.

FIG. 9 shows an example of a method for switching of multicast and broadcast service between multicast and unicast in a wireless communication system.

FIGS. 10A, 10B, 10C, and 10D show an example of a procedure for switching of multicast and broadcast service between multicast and unicast in a wireless communication system, according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

The following techniques, apparatuses, and systems may be applied to a variety of wireless multiple access systems. Examples of the multiple access systems include a code division multiple access (CDMA) system, a frequency division multiple access (FDMA) system, a time division multiple access (TDMA) system, an orthogonal frequency division multiple access (OFDMA) system, a single carrier frequency division multiple access (SC-FDMA) system, and a multicarrier frequency division multiple access (MC-FDMA) system. CDMA may be embodied through radio technology such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA may be embodied through radio technology such as global system for mobile communications (GSM), general packet radio service (GPRS), or enhanced data rates for GSM evolution (EDGE). OFDMA may be embodied through radio technology such as institute of electrical and electronics engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, or evolved UTRA (E-UTRA). UTRA is a part of a universal mobile telecommunications system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employs OFDMA in DL and SC-FDMA in UL. LTE-advanced (LTE-A) is an evolved version of 3GPP LTE.

For convenience of description, implementations of the present disclosure are mainly described in regards to a 3GPP based wireless communication system. However, the technical features of the present disclosure are not limited thereto. For example, although the following detailed description is given based on a mobile communication system corresponding to a 3GPP based wireless communication system, aspects of the present disclosure that are not limited to 3GPP based wireless communication system are applicable to other mobile communication systems.

For terms and technologies which are not specifically described among the terms of and technologies employed in the present disclosure, the wireless communication standard documents published before the present disclosure may be referenced.

In the present disclosure, “A or B” may mean “only A”, “only B”, or “both A and B”. In other words, “A or B” in the present disclosure may be interpreted as “A and/or B”. For example, “A, B or C” in the present disclosure may mean “only A”, “only B”, “only C”, or “any combination of A, B and C”.

In the present disclosure, slash (/) or comma (,) may mean “and/or”. For example, “A/B” may mean “A and/or B”. Accordingly, “A/B” may mean “only A”, “only B”, or “both A and B”. For example, “A, B, C” may mean “A, B or C”.

In the present disclosure, “at least one of A and B” may mean “only A”, “only B” or “both A and B”. In addition, the expression “at least one of A or B” or “at least one of A and/or B” in the present disclosure may be interpreted as same as “at least one of A and B”.

In addition, in the present disclosure, “at least one of A, B and C” may mean “only A”, “only B”, “only C”, or “any combination of A, B and C”. In addition, “at least one of A, B or C” or “at least one of A, B and/or C” may mean “at least one of A, B and C”.

Also, parentheses used in the present disclosure may mean “for example”. In detail, when it is shown as “control information (PDCCH)”, “PDCCH” may be proposed as an example of “ control information” . In other words, “ control information” in the present disclosure is not limited to “PDCCH”, and “PDDCH” may be proposed as an example of “control information”. In addition, even when shown as “control information (i.e., PDCCH)”, “PDCCH” may be proposed as an example of “control information”.

Technical features that are separately described in one drawing in the present disclosure may be implemented separately or simultaneously.

Although not limited thereto, various descriptions, functions, procedures, suggestions, methods and/or operational flowcharts of the present disclosure disclosed herein can be applied to various fields requiring wireless communication and/or connection (e.g., 5G) between devices.

Hereinafter, the present disclosure will be described in more detail with reference to drawings. The same reference numerals in the following drawings and/or descriptions may refer to the same and/or corresponding hardware blocks, software blocks, and/or functional blocks unless otherwise indicated.

FIG. 1 shows an example of a communication system to which implementations of the present disclosure is applied.

The 5G usage scenarios shown in FIG. 1 are only exemplary, and the technical features of the present disclosure can be applied to other 5G usage scenarios which are not shown in FIG. 1 .

Three main requirement categories for 5G include (1) a category of enhanced mobile broadband (eMBB), (2) a category of massive machine type communication (mMTC), and (3) a category of ultra-reliable and low latency communications (URLLC).

Partial use cases may require a plurality of categories for optimization and other use cases may focus only upon one key performance indicator (KPI). 5G supports such various use cases using a flexible and reliable method.

eMBB far surpasses basic mobile Internet access and covers abundant bidirectional work and media and entertainment applications in cloud and augmented reality. Data is one of 5G core motive forces and, in a 5G era, a dedicated voice service may not be provided for the first time. In 5G, it is expected that voice will be simply processed as an application program using data connection provided by a communication system. Main causes for increased traffic volume are due to an increase in the size of content and an increase in the number of applications requiring high data transmission rate. A streaming service (of audio and video), conversational video, and mobile Internet access will be more widely used as more devices are connected to the Internet. These many application programs require connectivity of an always turned-on state in order to push real-time information and alarm for users. Cloud storage and applications are rapidly increasing in a mobile communication platform and may be applied to both work and entertainment. The cloud storage is a special use case which accelerates growth of uplink data transmission rate. 5G is also used for remote work of cloud. When a tactile interface is used, 5G demands much lower end-to-end latency to maintain user good experience. Entertainment, for example, cloud gaming and video streaming, is another core element which increases demand for mobile broadband capability. Entertainment is essential for a smartphone and a tablet in any place including high mobility environments such as a train, a vehicle, and an airplane. Other use cases are augmented reality for entertainment and information search. In this case, the augmented reality requires very low latency and instantaneous data volume.

In addition, one of the most expected 5G use cases relates a function capable of smoothly connecting embedded sensors in all fields, i.e., mMTC. It is expected that the number of potential Internet-of-things (IoT) devices will reach 204 hundred million up to the year of 2020. An industrial IoT is one of categories of performing a main role enabling a smart city, asset tracking, smart utility, agriculture, and security infrastructure through 5G.

URLLC includes a new service that will change industry through remote control of main infrastructure and an ultra-reliable/available low-latency link such as a self-driving vehicle. A level of reliability and latency is essential to control a smart grid, automatize industry, achieve robotics, and control and adjust a drone.

5G is a means of providing streaming evaluated as a few hundred megabits per second to gigabits per second and may complement fiber-to-the-home (FTTH) and cable-based broadband (or DOCSIS). Such fast speed is needed to deliver TV in resolution of 4K or more (6K, 8K, and more), as well as virtual reality and augmented reality. Virtual reality (VR) and augmented reality (AR) applications include almost immersive sports games. A specific application program may require a special network configuration. For example, for VR games, gaming companies need to incorporate a core server into an edge network server of a network operator in order to minimize latency.

Automotive is expected to be a new important motivated force in 5G together with many use cases for mobile communication for vehicles. For example, entertainment for passengers requires high simultaneous capacity and mobile broadband with high mobility. This is because future users continue to expect connection of high quality regardless of their locations and speeds. Another use case of an automotive field is an AR dashboard. The AR dashboard causes a driver to identify an object in the dark in addition to an object seen from a front window and displays a distance from the object and a movement of the object by overlapping information talking to the driver. In the future, a wireless module enables communication between vehicles, information exchange between a vehicle and supporting infrastructure, and information exchange between a vehicle and other connected devices (e.g., devices accompanied by a pedestrian). A safety system guides alternative courses of a behavior so that a driver may drive more safely drive, thereby lowering the danger of an accident. The next stage will be a remotely controlled or self-driven vehicle. This requires very high reliability and very fast communication between different self-driven vehicles and between a vehicle and infrastructure. In the future, a self-driven vehicle will perform all driving activities and a driver will focus only upon abnormal traffic that the vehicle cannot identify. Technical requirements of a self-driven vehicle demand ultra-low latency and ultra-high reliability so that traffic safety is increased to a level that cannot be achieved by human being.

A smart city and a smart home/building mentioned as a smart society will be embedded in a high-density wireless sensor network. A distributed network of an intelligent sensor will identify conditions for costs and energy-efficient maintenance of a city or a home. Similar configurations may be performed for respective households. All of temperature sensors, window and heating controllers, burglar alarms, and home appliances are wirelessly connected. Many of these sensors are typically low in data transmission rate, power, and cost. However, real-time HD video may be demanded by a specific type of device to perform monitoring.

Consumption and distribution of energy including heat or gas is distributed at a higher level so that automated control of the distribution sensor network is demanded. The smart grid collects information and connects the sensors to each other using digital information and communication technology so as to act according to the collected information. Since this information may include behaviors of a supply company and a consumer, the smart grid may improve distribution of fuels such as electricity by a method having efficiency, reliability, economic feasibility, production sustainability, and automation. The smart grid may also be regarded as another sensor network having low latency.

Mission critical application (e.g., e-health) is one of 5G use scenarios. A health part contains many application programs capable of enjoying benefit of mobile communication. A communication system may support remote treatment that provides clinical treatment in a faraway place. Remote treatment may aid in reducing a barrier against distance and improve access to medical services that cannot be continuously available in a faraway rural area. Remote treatment is also used to perform important treatment and save lives in an emergency situation. The wireless sensor network based on mobile communication may provide remote monitoring and sensors for parameters such as heart rate and blood pressure.

Wireless and mobile communication gradually becomes important in the field of an industrial application. Wiring is high in installation and maintenance cost. Therefore, a possibility of replacing a cable with reconstructible wireless links is an attractive opportunity in many industrial fields. However, in order to achieve this replacement, it is necessary for wireless connection to be established with latency, reliability, and capacity similar to those of the cable and management of wireless connection needs to be simplified. Low latency and a very low error probability are new requirements when connection to 5G is needed.

Logistics and freight tracking are important use cases for mobile communication that enables inventory and package tracking anywhere using a location-based information system. The use cases of logistics and freight typically demand low data rate but require location information with a wide range and reliability.

Referring to FIG. 1 , the communication system 1 includes wireless devices 100 a to 100 f, base stations (BSs) 200, and a network 300. Although FIG. 1 illustrates a 5G network as an example of the network of the communication system 1, the implementations of the present disclosure are not limited to the 5G system, and can be applied to the future communication system beyond the 5G system.

The BSs 200 and the network 300 may be implemented as wireless devices and a specific wireless device may operate as a BS/network node with respect to other wireless devices.

The wireless devices 100 a to 100 f represent devices performing communication using radio access technology (RAT) (e.g., 5G new RAT (NR)) or LTE) and may be referred to as communication/radio/5G devices. The wireless devices 100 a to 100 f may include, without being limited to, a robot 100 a, vehicles 100 b-1 and 100 b-2, an extended reality (XR) device 100 c, a hand-held device 100 d, a home appliance 100 e, an IoT device 100 f, and an artificial intelligence (AI) device/server 400. For example, the vehicles may include a vehicle having a wireless communication function, an autonomous driving vehicle, and a vehicle capable of performing communication between vehicles. The vehicles may include an unmanned aerial vehicle (UAV) (e.g., a drone). The XR device may include an AR/VR/Mixed Reality (MR) device and may be implemented in the form of a head-mounted device (HMD), a head-up display (HUD) mounted in a vehicle, a television, a smartphone, a computer, a wearable device, a home appliance device, a digital signage, a vehicle, a robot, etc. The hand-held device may include a smartphone, a smartpad, a wearable device (e.g., a smartwatch or a smartglasses), and a computer (e.g., a notebook). The home appliance may include a TV, a refrigerator, and a washing machine. The IoT device may include a sensor and a smartmeter.

In the present disclosure, the wireless devices 100 a to 100 f may be called user equipments (UEs). A UE may include, for example, a cellular phone, a smartphone, a laptop computer, a digital broadcast terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation system, a slate personal computer (PC), a tablet PC, an ultrabook, a vehicle, a vehicle having an autonomous traveling function, a connected car, an UAV, an AI module, a robot, an AR device, a VR device, an MR device, a hologram device, a public safety device, an MTC device, an IoT device, a medical device, a FinTech device (or a financial device), a security device, a weather/environment device, a device related to a 5G service, or a device related to a fourth industrial revolution field.

The UAV may be, for example, an aircraft aviated by a wireless control signal without a human being onboard.

The VR device may include, for example, a device for implementing an object or a background of the virtual world. The AR device may include, for example, a device implemented by connecting an object or a background of the virtual world to an object or a background of the real world. The MR device may include, for example, a device implemented by merging an object or a background of the virtual world into an object or a background of the real world. The hologram device may include, for example, a device for implementing a stereoscopic image of 360 degrees by recording and reproducing stereoscopic information, using an interference phenomenon of light generated when two laser lights called holography meet.

The public safety device may include, for example, an image relay device or an image device that is wearable on the body of a user.

The MTC device and the IoT device may be, for example, devices that do not require direct human intervention or manipulation. For example, the MTC device and the IoT device may include smartmeters, vending machines, thermometers, smartbulbs, door locks, or various sensors.

The medical device may be, for example, a device used for the purpose of diagnosing, treating, relieving, curing, or preventing disease. For example, the medical device may be a device used for the purpose of diagnosing, treating, relieving, or correcting injury or impairment. For example, the medical device may be a device used for the purpose of inspecting, replacing, or modifying a structure or a function. For example, the medical device may be a device used for the purpose of adjusting pregnancy. For example, the medical device may include a device for treatment, a device for operation, a device for (in vitro) diagnosis, a hearing aid, or a device for procedure.

The security device may be, for example, a device installed to prevent a danger that may arise and to maintain safety. For example, the security device may be a camera, a closed-circuit TV (CCTV), a recorder, or a black box.

The FinTech device may be, for example, a device capable of providing a financial service such as mobile payment. For example, the FinTech device may include a payment device or a point of sales (POS) system.

The weather/environment device may include, for example, a device for monitoring or predicting a weather/environment.

The wireless devices 100 a to 100 f may be connected to the network 300 via the BSs 200. An AI technology may be applied to the wireless devices 100 a to 100 f and the wireless devices 100 a to 100 f may be connected to the AI server 400 via the network 300. The network 300 may be configured using a 3G network, a 4G (e.g., LTE) network, a 5G (e.g., NR) network, and a beyond-5G network. Although the wireless devices 100 a to 100 f may communicate with each other through the BSs 200/network 300, the wireless devices 100 a to 100 f may perform direct communication (e.g., sidelink communication) with each other without passing through the BSs 200/network 300. For example, the vehicles 100 b-1 and 100 b-2 may perform direct communication (e.g., vehicle-to-vehicle (V2V)/vehicle-to-everything (V2X) communication). The IoT device (e.g., a sensor) may perform direct communication with other IoT devices (e.g., sensors) or other wireless devices 100 a to 100 f.

Wireless communication/connections 150 a, 150 b and 150 c may be established between the wireless devices 100 a to 100 f and/or between wireless device 100 a to 100 f and BS 200 and/or between BSs 200. Herein, the wireless communication/connections may be established through various RATs (e.g., 5G NR) such as uplink/downlink communication 150 a, sidelink communication (or device-to-device (D2D) communication) 150 b, inter-base station communication 150 c (e.g., relay, integrated access and backhaul (IAB)), etc. The wireless devices 100 a to 100 f and the BSs 200/the wireless devices 100 a to 100 f may transmit/receive radio signals to/from each other through the wireless communication/connections 150 a, 150 b and 150 c. For example, the wireless communication/connections 150 a, 150 b and 150 c may transmit/receive signals through various physical channels. To this end, at least a part of various configuration information configuring processes, various signal processing processes (e.g., channel encoding/decoding, modulation/demodulation, and resource mapping/de-mapping), and resource allocating processes, for transmitting/receiving radio signals, may be performed based on the various proposals of the present disclosure.

AI refers to the field of studying artificial intelligence or the methodology that can create it, and machine learning refers to the field of defining various problems addressed in the field of AI and the field of methodology to solve them. Machine learning is also defined as an algorithm that increases the performance of a task through steady experience on a task.

Robot means a machine that automatically processes or operates a given task by its own ability. In particular, robots with the ability to recognize the environment and make self-determination to perform actions can be called intelligent robots. Robots can be classified as industrial, medical, home, military, etc., depending on the purpose or area of use. The robot can perform a variety of physical operations, such as moving the robot joints with actuators or motors. The movable robot also includes wheels, brakes, propellers, etc., on the drive, allowing it to drive on the ground or fly in the air.

Autonomous driving means a technology that drives on its own, and autonomous vehicles mean vehicles that drive without user's control or with minimal user's control. For example, autonomous driving may include maintaining lanes in motion, automatically adjusting speed such as adaptive cruise control, automatic driving along a set route, and automatically setting a route when a destination is set. The vehicle covers vehicles equipped with internal combustion engines, hybrid vehicles equipped with internal combustion engines and electric motors, and electric vehicles equipped with electric motors, and may include trains, motorcycles, etc., as well as cars. Autonomous vehicles can be seen as robots with autonomous driving functions.

Extended reality is collectively referred to as VR, AR, and MR. VR technology provides objects and backgrounds of real world only through computer graphic (CG) images. AR technology provides a virtual CG image on top of a real object image. MR technology is a CG technology that combines and combines virtual objects into the real world. MR technology is similar to AR technology in that they show real and virtual objects together. However, there is a difference in that in AR technology, virtual objects are used as complementary forms to real objects, while in MR technology, virtual objects and real objects are used as equal personalities.

NR supports multiples numerologies (and/or multiple subcarrier spacings (SCS)) to support various 5G services. For example, if SCS is 15 kHz, wide area can be supported in traditional cellular bands, and if SCS is 30 kHz/60 kHz, dense-urban, lower latency, and wider carrier bandwidth can be supported. If SCS is 60 kHz or higher, bandwidths greater than 24.25 GHz can be supported to overcome phase noise.

The NR frequency band may be defined as two types of frequency range, i.e., FR1 and FR2. The numerical value of the frequency range may be changed. For example, the frequency ranges of the two types (FR1 and FR2) may be as shown in Table 1 below. For ease of explanation, in the frequency ranges used in the NR system, FR1 may mean “sub 6 GHz range”, FR2 may mean “above 6 GHz range,” and may be referred to as millimeter wave (mmW).

TABLE 1 Frequency Range Corresponding frequency designation range Subcarrier Spacing FR1  450 MHz-6000 MHz  15, 30, 60 kHz FR2 24250 MHz-52600 MHz 60, 120, 240 kHz

As mentioned above, the numerical value of the frequency range of the NR system may be changed. For example, FR1 may include a frequency band of 410 MHz to 7125 MHz as shown in Table 2 below. That is, FR1 may include a frequency band of 6GHz (or 5850, 5900, 5925 MHz, etc.) or more. For example, a frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or more included in FR1 may include an unlicensed band. Unlicensed bands may be used for a variety of purposes, for example for communication for vehicles (e.g., autonomous driving).

TABLE 2 Frequency Range Corresponding frequency designation range Subcarrier Spacing FR1  410 MHz-7125 MHz  15, 30, 60 kHz FR2 24250 MHz-52600 MHz 60, 120, 240 kHz

Here, the radio communication technologies implemented in the wireless devices in the present disclosure may include narrowband internet-of-things (NB-IoT) technology for low-power communication as well as LTE, NR and 6G. For example, NB-IoT technology may be an example of low power wide area network (LPWAN) technology, may be implemented in specifications such as LTE Cat NB1 and/or LTE Cat NB2, and may not be limited to the above-mentioned names. Additionally and/or alternatively, the radio communication technologies implemented in the wireless devices in the present disclosure may communicate based on LTE-M technology. For example, LTE-M technology may be an example of LPWAN technology and be called by various names such as enhanced machine type communication (eMTC). For example, LTE-M technology may be implemented in at least one of the various specifications, such as 1) LTE Cat 0, 2) LTE Cat M1, 3) LTE Cat M2, 4) LTE non-bandwidth limited (non-BL), 5) LTE-MTC, 6) LTE Machine Type Communication, and/or 7) LTE M, and may not be limited to the above-mentioned names. Additionally and/or alternatively, the radio communication technologies implemented in the wireless devices in the present disclosure may include at least one of ZigBee, Bluetooth, and/or LPWAN which take into account low-power communication, and may not be limited to the above-mentioned names. For example, ZigBee technology may generate personal area networks (PANs) associated with small/low-power digital communication based on various specifications such as IEEE 802.15.4 and may be called various names.

FIG. 2 shows an example of wireless devices to which implementations of the present disclosure is applied.

Referring to FIG. 2 , a first wireless device 100 and a second wireless device 200 may transmit/receive radio signals to/from an external device through a variety of RATs (e.g., LTE and NR).

In FIG. 2 , {the first wireless device 100 and the second wireless device 200} may correspond to at least one of {the wireless device 100 a to 100 f and the BS 200}, {the wireless device 100 a to 100 f and the wireless device 100 a to 100 f} and/or {the BS 200 and the BS 200} of FIG. 1 .

The first wireless device 100 may include at least one transceiver, such as a transceiver 106, at least one processing chip, such as a processing chip 101, and/or one or more antennas 108.

The processing chip 101 may include at least one processor, such a processor 102, and at least one memory, such as a memory 104. It is exemplarily shown in FIG. 2 that the memory 104 is included in the processing chip 101. Additional and/or alternatively, the memory 104 may be placed outside of the processing chip 101.

The processor 102 may control the memory 104 and/or the transceiver 106 and may be configured to implement the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts described in the present disclosure. For example, the processor 102 may process information within the memory 104 to generate first information/signals and then transmit radio signals including the first information/signals through the transceiver 106. The processor 102 may receive radio signals including second information/signals through the transceiver 106 and then store information obtained by processing the second information/signals in the memory 104.

The memory 104 may be operably connectable to the processor 102. The memory 104 may store various types of information and/or instructions. The memory 104 may store a software code 105 which implements instructions that, when executed by the processor 102, perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. For example, the software code 105 may implement instructions that, when executed by the processor 102, perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. For example, the software code 105 may control the processor 102 to perform one or more protocols. For example, the software code 105 may control the processor 102 to perform one or more layers of the radio interface protocol.

Herein, the processor 102 and the memory 104 may be a part of a communication modem/circuit/chip designed to implement RAT (e.g., LTE or NR). The transceiver 106 may be connected to the processor 102 and transmit and/or receive radio signals through one or more antennas 108. Each of the transceiver 106 may include a transmitter and/or a receiver. The transceiver 106 may be interchangeably used with radio frequency (RF) unit(s). In the present disclosure, the first wireless device 100 may represent a communication modem/circuit/chip.

The second wireless device 200 may include at least one transceiver, such as a transceiver 206, at least one processing chip, such as a processing chip 201, and/or one or more antennas 208.

The processing chip 201 may include at least one processor, such a processor 202, and at least one memory, such as a memory 204. It is exemplarily shown in FIG. 2 that the memory 204 is included in the processing chip 201. Additional and/or alternatively, the memory 204 may be placed outside of the processing chip 201.

The processor 202 may control the memory 204 and/or the transceiver 206 and may be configured to implement the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts described in the present disclosure. For example, the processor 202 may process information within the memory 204 to generate third information/signals and then transmit radio signals including the third information/signals through the transceiver 206.

The processor 202 may receive radio signals including fourth information/signals through the transceiver 106 and then store information obtained by processing the fourth information/signals in the memory 204.

The memory 204 may be operably connectable to the processor 202. The memory 204 may store various types of information and/or instructions. The memory 204 may store a software code 205 which implements instructions that, when executed by the processor 202, perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. For example, the software code 205 may implement instructions that, when executed by the processor 202, perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. For example, the software code 205 may control the processor 202 to perform one or more protocols. For example, the software code 205 may control the processor 202 to perform one or more layers of the radio interface protocol.

Herein, the processor 202 and the memory 204 may be a part of a communication modem/circuit/chip designed to implement RAT (e.g., LTE or NR). The transceiver 206 may be connected to the processor 202 and transmit and/or receive radio signals through one or more antennas 208. Each of the transceiver 206 may include a transmitter and/or a receiver. The transceiver 206 may be interchangeably used with RF unit. In the present disclosure, the second wireless device 200 may represent a communication modem/circuit/chip.

Hereinafter, hardware elements of the wireless devices 100 and 200 will be described more specifically. One or more protocol layers may be implemented by, without being limited to, one or more processors 102 and 202. For example, the one or more processors 102 and 202 may implement one or more layers (e.g., functional layers such as physical (PHY) layer, media access control (MAC) layer, radio link control (RLC) layer, packet data convergence protocol (PDCP) layer, radio resource control (RRC) layer, and service data adaptation protocol (SDAP) layer). The one or more processors 102 and 202 may generate one or more protocol data units (PDUs) and/or one or more service data unit (SDUs) according to the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. The one or more processors 102 and 202 may generate messages, control information, data, or information according to the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. The one or more processors 102 and 202 may generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data, or information according to the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure and provide the generated signals to the one or more transceivers 106 and 206. The one or more processors 102 and 202 may receive the signals (e.g., baseband signals) from the one or more transceivers 106 and 206 and acquire the PDUs, SDUs, messages, control information, data, or information according to the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure.

The one or more processors 102 and 202 may be referred to as controllers, microcontrollers, microprocessors, or microcomputers. The one or more processors 102 and 202 may be implemented by hardware, firmware, software, or a combination thereof. As an example, one or more application specific integrated circuits (ASICs), one or more digital signal processors (DSPs), one or more digital signal processing devices (DSPDs), one or more programmable logic devices (PLDs), or one or more field programmable gate arrays (FPGAs) may be included in the one or more processors 102 and 202. The descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure may be implemented using firmware or software and the firmware or software may be configured to include the modules, procedures, or functions. Firmware or software configured to perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure may be included in the one or more processors 102 and 202 or stored in the one or more memories 104 and 204 so as to be driven by the one or more processors 102 and 202. The descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure may be implemented using firmware or software in the form of code, commands, and/or a set of commands.

The one or more memories 104 and 204 may be connected to the one or more processors 102 and 202 and store various types of data, signals, messages, information, programs, code, instructions, and/or commands. The one or more memories 104 and 204 may be configured by read-only memories (ROMs), random access memories (RAMs), electrically erasable programmable read-only memories (EPROMs), flash memories, hard drives, registers, cash memories, computer-readable storage media, and/or combinations thereof. The one or more memories 104 and 204 may be located at the interior and/or exterior of the one or more processors 102 and 202. The one or more memories 104 and 204 may be connected to the one or more processors 102 and 202 through various technologies such as wired or wireless connection.

The one or more transceivers 106 and 206 may transmit user data, control information, and/or radio signals/channels, mentioned in the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure, to one or more other devices. The one or more transceivers 106 and 206 may receive user data, control information, and/or radio signals/channels, mentioned in the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure, from one or more other devices. For example, the one or more transceivers 106 and 206 may be connected to the one or more processors 102 and 202 and transmit and receive radio signals. For example, the one or more processors 102 and 202 may perform control so that the one or more transceivers 106 and 206 may transmit user data, control information, or radio signals to one or more other devices. The one or more processors 102 and 202 may perform control so that the one or more transceivers 106 and 206 may receive user data, control information, or radio signals from one or more other devices.

The one or more transceivers 106 and 206 may be connected to the one or more antennas 108 and 208 and the one or more transceivers 106 and 206 may be configured to transmit and receive user data, control information, and/or radio signals/channels, mentioned in the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure, through the one or more antennas 108 and 208. In the present disclosure, the one or more antennas may be a plurality of physical antennas or a plurality of logical antennas (e.g., antenna ports).

The one or more transceivers 106 and 206 may convert received radio signals/channels, etc., from RF band signals into baseband signals in order to process received user data, control information, radio signals/channels, etc., using the one or more processors 102 and 202. The one or more transceivers 106 and 206 may convert the user data, control information, radio signals/channels, etc., processed using the one or more processors 102 and 202 from the base band signals into the RF band signals. To this end, the one or more transceivers 106 and 206 may include (analog) oscillators and/or filters. For example, the transceivers 106 and 206 can up-convert OFDM baseband signals to a carrier frequency by their (analog) oscillators and/or filters under the control of the processors 102 and 202 and transmit the up-converted OFDM signals at the carrier frequency. The transceivers 106 and 206 may receive OFDM signals at a carrier frequency and down-convert the OFDM signals into OFDM baseband signals by their (analog) oscillators and/or filters under the control of the transceivers 102 and 202.

In the implementations of the present disclosure, a UE may operate as a transmitting device in uplink (UL) and as a receiving device in downlink (DL). In the implementations of the present disclosure, a BS may operate as a receiving device in UL and as a transmitting device in DL. Hereinafter, for convenience of description, it is mainly assumed that the first wireless device 100 acts as the UE, and the second wireless device 200 acts as the BS. For example, the processor(s) 102 connected to, mounted on or launched in the first wireless device 100 may be configured to perform the UE behavior according to an implementation of the present disclosure or control the transceiver(s) 106 to perform the UE behavior according to an implementation of the present disclosure. The processor(s) 202 connected to, mounted on or launched in the second wireless device 200 may be configured to perform the BS behavior according to an implementation of the present disclosure or control the transceiver(s) 206 to perform the BS behavior according to an implementation of the present disclosure.

In the present disclosure, a BS is also referred to as a node B (NB), an eNode B (eNB), or a gNB.

FIG. 3 shows an example of a wireless device to which implementations of the present disclosure is applied.

The wireless device may be implemented in various forms according to a use-case/service (refer to FIG. 1 ).

Referring to FIG. 3 , wireless devices 100 and 200 may correspond to the wireless devices 100 and 200 of FIG. 2 and may be configured by various elements, components, units/portions, and/or modules. For example, each of the wireless devices 100 and 200 may include a communication unit 110, a control unit 120, a memory unit 130, and additional components 140. The communication unit 110 may include a communication circuit 112 and transceiver(s) 114. For example, the communication circuit 112 may include the one or more processors 102 and 202 of FIG. 2 and/or the one or more memories 104 and 204 of FIG. 2 . For example, the transceiver(s) 114 may include the one or more transceivers 106 and 206 of FIG. 2 and/or the one or more antennas 108 and 208 of FIG. 2 . The control unit 120 is electrically connected to the communication unit 110, the memory 130, and the additional components 140 and controls overall operation of each of the wireless devices 100 and 200. For example, the control unit 120 may control an electric/mechanical operation of each of the wireless devices 100 and 200 based on programs/code/commands/information stored in the memory unit 130. The control unit 120 may transmit the information stored in the memory unit 130 to the exterior (e.g., other communication devices) via the communication unit 110 through a wireless/wired interface or store, in the memory unit 130, information received through the wireless/wired interface from the exterior (e.g., other communication devices) via the communication unit 110.

The additional components 140 may be variously configured according to types of the wireless devices 100 and 200. For example, the additional components 140 may include at least one of a power unit/battery, input/output (I/O) unit (e.g., audio I/O port, video I/O port), a driving unit, and a computing unit. The wireless devices 100 and 200 may be implemented in the form of, without being limited to, the robot (100 a of FIG. 1 ), the vehicles (100 b-1 and 100 b-2 of FIG. 1 ), the XR device (100 c of FIG. 1 ), the hand-held device (100 d of FIG. 1 ), the home appliance (100 e of FIG. 1 ), the IoT device (100 f of FIG. 1 ), a digital broadcast terminal, a hologram device, a public safety device, an MTC device, a medicine device, a FinTech device (or a finance device), a security device, a climate/environment device, the AI server/device (400 of FIG. 1 ), the BSs (200 of FIG. 1 ), a network node, etc. The wireless devices 100 and 200 may be used in a mobile or fixed place according to a use-example/service.

In FIG. 3 , the entirety of the various elements, components, units/portions, and/or modules in the wireless devices 100 and 200 may be connected to each other through a wired interface or at least a part thereof may be wirelessly connected through the communication unit 110. For example, in each of the wireless devices 100 and 200, the control unit 120 and the communication unit 110 may be connected by wire and the control unit 120 and first units (e.g., 130 and 140) may be wirelessly connected through the communication unit 110. Each element, component, unit/portion, and/or module within the wireless devices 100 and 200 may further include one or more elements. For example, the control unit 120 may be configured by a set of one or more processors. As an example, the control unit 120 may be configured by a set of a communication control processor, an application processor (AP), an electronic control unit (ECU), a graphical processing unit, and a memory control processor. As another example, the memory 130 may be configured by a RAM, a DRAM, a ROM, a flash memory, a volatile memory, a non-volatile memory, and/or a combination thereof

FIG. 4 shows an example of UE to which implementations of the present disclosure is applied.

Referring to FIG. 4 , a UE 100 may correspond to the first wireless device 100 of FIG. 2 and/or the wireless device 100 or 200 of FIG. 3 .

A UE 100 includes a processor 102, a memory 104, a transceiver 106, one or more antennas 108, a power management module 110, a battery 1112, a display 114, a keypad 116, a subscriber identification module (SIM) card 118, a speaker 120, and a microphone 122.

The processor 102 may be configured to implement the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. The processor 102 may be configured to control one or more other components of the UE 100 to implement the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. Layers of the radio interface protocol may be implemented in the processor 102. The processor 102 may include ASIC, other chipset, logic circuit and/or data processing device. The processor 102 may be an application processor.

The processor 102 may include at least one of a digital signal processor (DSP), a central processing unit (CPU), a graphics processing unit (GPU), a modem (modulator and demodulator). An example of the processor 102 may be found in SNAPDRAGON™ series of processors made by Qualcomm®, EXYNOS™ series of processors made by Samsung®, A series of processors made by Apple®, HELIO™ series of processors made by MediaTek®, ATOM™ series of processors made by Intel® or a corresponding next generation processor.

The memory 104 is operatively coupled with the processor 102 and stores a variety of information to operate the processor 102. The memory 104 may include ROM, RAM, flash memory, memory card, storage medium and/or other storage device. When the embodiments are implemented in software, the techniques described herein can be implemented with modules (e.g., procedures, functions, etc.) that perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. The modules can be stored in the memory 104 and executed by the processor 102. The memory 104 can be implemented within the processor 102 or external to the processor 102 in which case those can be communicatively coupled to the processor 102 via various means as is known in the art.

The transceiver 106 is operatively coupled with the processor 102, and transmits and/or receives a radio signal. The transceiver 106 includes a transmitter and a receiver. The transceiver 106 may include baseband circuitry to process radio frequency signals. The transceiver 106 controls the one or more antennas 108 to transmit and/or receive a radio signal.

The power management module 110 manages power for the processor 102 and/or the transceiver 106. The battery 112 supplies power to the power management module 110.

The display 114 outputs results processed by the processor 102. The keypad 116 receives inputs to be used by the processor 102. The keypad 16 may be shown on the display 114.

The SIM card 118 is an integrated circuit that is intended to securely store the international mobile subscriber identity (IMSI) number and its related key, which are used to identify and authenticate subscribers on mobile telephony devices (such as mobile phones and computers). It is also possible to store contact information on many SIM cards.

The speaker 120 outputs sound-related results processed by the processor 102. The microphone 122 receives sound-related inputs to be used by the processor 102.

FIGS. 5 and 6 show an example of protocol stacks in a 3GPP based wireless communication system to which implementations of the present disclosure is applied.

In particular, FIG. 5 illustrates an example of a radio interface user plane protocol stack between a UE and a BS and FIG. 6 illustrates an example of a radio interface control plane protocol stack between a UE and a BS. The control plane refers to a path through which control messages used to manage call by a UE and a network are transported. The user plane refers to a path through which data generated in an application layer, for example, voice data or Internet packet data are transported. Referring to FIG. 5 , the user plane protocol stack may be divided into Layer 1 (i.e., a PHY layer) and Layer 2. Referring to FIG. 6, the control plane protocol stack may be divided into Layer 1 (i.e., a PHY layer), Layer 2, Layer 3 (e.g., an RRC layer), and a non-access stratum (NAS) layer. Layer 1, Layer 2 and Layer 3 are referred to as an access stratum (AS).

In the 3GPP LTE system, the Layer 2 is split into the following sublayers: MAC, RLC, and PDCP. In the 3GPP NR system, the Layer 2 is split into the following sublayers: MAC, RLC, PDCP and SDAP. The PHY layer offers to the MAC sublayer transport channels, the MAC sublayer offers to the RLC sublayer logical channels, the RLC sublayer offers to the PDCP sublayer RLC channels, the PDCP sublayer offers to the SDAP sublayer radio bearers. The SDAP sublayer offers to 5G core network quality of service (QoS) flows.

In the 3GPP NR system, the main services and functions of the MAC sublayer include: mapping between logical channels and transport channels; multiplexing/de-multiplexing of MAC SDUs belonging to one or different logical channels into/from transport blocks (TB) delivered to/from the physical layer on transport channels; scheduling information reporting; error correction through hybrid automatic repeat request (HARQ) (one HARQ entity per cell in case of carrier aggregation (CA)); priority handling between UEs by means of dynamic scheduling; priority handling between logical channels of one UE by means of logical channel prioritization; padding. A single MAC entity may support multiple numerologies, transmission timings and cells. Mapping restrictions in logical channel prioritization control which numerology(ies), cell(s), and transmission timing(s) a logical channel can use.

Different kinds of data transfer services are offered by MAC. To accommodate different kinds of data transfer services, multiple types of logical channels are defined, i.e., each supporting transfer of a particular type of information. Each logical channel type is defined by what type of information is transferred. Logical channels are classified into two groups: control channels and traffic channels. Control channels are used for the transfer of control plane information only, and traffic channels are used for the transfer of user plane information only. Broadcast control channel (BCCH) is a downlink logical channel for broadcasting system control information, paging control channel (PCCH) is a downlink logical channel that transfers paging information, system information change notifications and indications of ongoing public warning service (PWS) broadcasts, common control channel (CCCH) is a logical channel for transmitting control information between UEs and network and used for UEs having no RRC connection with the network, and dedicated control channel (DCCH) is a point-to-point bi-directional logical channel that transmits dedicated control information between a UE and the network and used by UEs having an RRC connection. Dedicated traffic channel (DTCH) is a point-to-point logical channel, dedicated to one UE, for the transfer of user information. A DTCH can exist in both uplink and downlink. In downlink, the following connections between logical channels and transport channels exist: BCCH can be mapped to broadcast channel (BCH); BCCH can be mapped to downlink shared channel (DL-SCH); PCCH can be mapped to paging channel (PCH); CCCH can be mapped to DL-SCH; DCCH can be mapped to DL-SCH; and DTCH can be mapped to DL-SCH. In uplink, the following connections between logical channels and transport channels exist: CCCH can be mapped to uplink shared channel (UL-SCH); DCCH can be mapped to UL-SCH; and DTCH can be mapped to UL-SCH.

The RLC sublayer supports three transmission modes: transparent mode (TM), unacknowledged mode (UM), and acknowledged node (AM). The RLC configuration is per logical channel with no dependency on numerologies and/or transmission durations. In the 3GPP NR system, the main services and functions of the RLC sublayer depend on the transmission mode and include: transfer of upper layer PDUs; sequence numbering independent of the one in PDCP (UM and AM); error correction through ARQ (AM only); segmentation (AM and UM) and re-segmentation (AM only) of RLC SDUs; reassembly of SDU (AM and UM); duplicate detection (AM only); RLC SDU discard (AM and UM); RLC re-establishment; protocol error detection (AM only).

In the 3GPP NR system, the main services and functions of the PDCP sublayer for the user plane include: sequence numbering; header compression and decompression using robust header compression (ROHC); transfer of user data; reordering and duplicate detection; in-order delivery; PDCP PDU routing (in case of split bearers); retransmission of PDCP SDUs; ciphering, deciphering and integrity protection; PDCP SDU discard; PDCP re-establishment and data recovery for RLC AM; PDCP status reporting for RLC AM; duplication of PDCP PDUs and duplicate discard indication to lower layers. The main services and functions of the PDCP sublayer for the control plane include: sequence numbering; ciphering, deciphering and integrity protection; transfer of control plane data; reordering and duplicate detection; in-order delivery; duplication of PDCP PDUs and duplicate discard indication to lower layers.

In the 3GPP NR system, the main services and functions of SDAP include: mapping between a QoS flow and a data radio bearer; marking QoS flow ID (QFI) in both DL and UL packets. A single protocol entity of SDAP is configured for each individual PDU session.

In the 3GPP NR system, the main services and functions of the RRC sublayer include: broadcast of system information related to AS and NAS; paging initiated by 5GC or NG-RAN; establishment, maintenance and release of an RRC connection between the UE and NG-RAN; security functions including key management; establishment, configuration, maintenance and release of signaling radio bearers (SRBs) and data radio bearers (DRBs); mobility functions (including: handover and context transfer, UE cell selection and reselection and control of cell selection and reselection, inter-RAT mobility); QoS management functions; UE measurement reporting and control of the reporting; detection of and recovery from radio link failure; NAS message transfer to/from NAS from/to UE.

FIG. 7 shows an example of the overall architecture of an NG-RAN to which technical features of the present disclosure can be applied.

Referring to FIG. 7 , a gNB may include a gNB-CU (hereinafter, gNB-CU may be simply referred to as CU) and at least one gNB-DU (hereinafter, gNB-DU may be simply referred to as DU).

The gNB-CU is a logical node hosting RRC, SDAP and PDCP protocols of the gNB or an RRC and PDCP protocols of the en-gNB. The gNB-CU controls the operation of the at least one gNB-DU.

The gNB-DU is a logical node hosting RLC, MAC, and physical layers of the gNB or the en-gNB. The operation of the gNB-DU is partly controlled by the gNB-CU. One gNB-DU supports one or multiple cells. One cell is supported by only one gNB-DU.

The gNB-CU and gNB-DU are connected via an F1 interface. The gNB-CU terminates the F1 interface connected to the gNB-DU. The gNB-DU terminates the F1 interface connected to the gNB-CU. One gNB-DU is connected to only one gNB-CU. However, the gNB-DU may be connected to multiple gNB-CUs by appropriate implementation. The F1 interface is a logical interface. For NG-RAN, the NG and Xn-C interfaces for a gNB consisting of a gNB-CU and gNB-DUs, terminate in the gNB-CU. For E-UTRAN-NR dual connectivity (EN-DC), the S1-U and X2-C interfaces for a gNB consisting of a gNB-CU and gNB-DUs, terminate in the gNB-CU. The gNB-CU and connected gNB-DUs are only visible to other gNBs and the 5GC as a gNB.

Functions of the F1 interface includes F1 control (F1-C) functions as follows.

(1) F1 Interface Management Function

The error indication function is used by the gNB-DU or gNB-CU to indicate to the gNB-CU or gNB-DU that an error has occurred.

The reset function is used to initialize the peer entity after node setup and after a failure event occurred. This procedure can be used by both the gNB-DU and the gNB-CU.

The F1 setup function allows to exchange application level data needed for the gNB-DU and gNB-CU to interoperate correctly on the F1 interface. The F1 setup is initiated by the gNB-DU.

The gNB-CU configuration update and gNB-DU configuration update functions allow to update application level configuration data needed between gNB-CU and gNB-DU to interoperate correctly over the F1 interface, and may activate or deactivate cells.

The F1 setup and gNB-DU configuration update functions allow to inform the single network slice selection assistance information (S-NSSAI) supported by the gNB-DU.

The F1 resource coordination function is used to transfer information about frequency resource sharing between gNB-CU and gNB-DU.

(2) System Information Management Function

Scheduling of system broadcast information is carried out in the gNB-DU. The gNB-DU is responsible for transmitting the system information according to the scheduling parameters available.

The gNB-DU is responsible for the encoding of NR master information block (MIB). In case broadcast of system information block type-1 (SIB1) and other SI messages is needed, the gNB-DU is responsible for the encoding of SIB1 and the gNB-CU is responsible for the encoding of other SI messages.

(3) F1 UE Context Management Function

The F1 UE context management function supports the establishment and modification of the necessary overall UE context.

The establishment of the F1 UE context is initiated by the gNB-CU and accepted or rejected by the gNB-DU based on admission control criteria (e.g., resource not available).

The modification of the F1 UE context can be initiated by either gNB-CU or gNB-DU.

The receiving node can accept or reject the modification. The F1 UE context management function also supports the release of the context previously established in the gNB-DU. The release of the context is triggered by the gNB-CU either directly or following a request received from the gNB-DU. The gNB-CU request the gNB-DU to release the UE Context when the UE enters RRC_IDLE or RRC_INACTIVE.

This function can be also used to manage DRBs and SRBs, i.e., establishing, modifying and releasing DRB and SRB resources. The establishment and modification of DRB resources are triggered by the gNB-CU and accepted/rejected by the gNB-DU based on resource reservation information and QoS information to be provided to the gNB-DU. For each DRB to be setup or modified, the S-NSSAI may be provided by gNB-CU to the gNB-DU in the UE context setup procedure and the UE context modification procedure.

The mapping between QoS flows and radio bearers is performed by gNB-CU and the granularity of bearer related management over F1 is radio bearer level. For NG-RAN, the gNB-CU provides an aggregated DRB QoS profile and QoS flow profile to the gNB-DU, and the gNB-DU either accepts the request or rejects it with appropriate cause value. To support packet duplication for intra-gNB-DU carrier aggregation (CA), one data radio bearer should be configured with two GPRS tunneling protocol (GTP)-U tunnels between gNB-CU and a gNB-DU.

With this function, gNB-CU requests the gNB-DU to setup or change of the special cell (SpCell) for the UE, and the gNB-DU either accepts or rejects the request with appropriate cause value.

With this function, the gNB-CU requests the setup of the secondary cell(s) (SCell(s)) at the gNB-DU side, and the gNB-DU accepts all, some or none of the SCell(s) and replies to the gNB-CU. The gNB-CU requests the removal of the SCell(s) for the UE.

(4) RRC Message Transfer Function

This function allows to transfer RRC messages between gNB-CU and gNB-DU. RRC messages are transferred over F1-C. The gNB-CU is responsible for the encoding of the dedicated RRC message with assistance information provided by gNB-DU.

(5) Paging Function

The gNB-DU is responsible for transmitting the paging information according to the scheduling parameters provided.

The gNB-CU provides paging information to enable the gNB-DU to calculate the exact paging occasion (PO) and paging frame (PF). The gNB-CU determines the paging assignment (PA). The gNB-DU consolidates all the paging records for a particular PO, PF and PA, and encodes the final RRC message and broadcasts the paging message on the respective PO, PF in the PA.

(6) Warning Messages Information Transfer Function

This function allows to cooperate with the warning message transmission procedures over NG interface. The gNB-CU is responsible for encoding the warning related SI message and sending it together with other warning related information for the gNB-DU to broadcast over the radio interface.

FIG. 8 shows an interface protocol structure for F1-C to which technical features of the present disclosure can be applied.

A transport network layer (TNL) is based on Internet protocol (IP) transport, comprising a stream control transmission protocol (SCTP) layer on top of the IP layer. An application layer signaling protocol is referred to as an F1 application protocol (E1AP).

Hereinafter, PDU Session Resource Setup and PDU Session Resource Modify are described. Section 8.2 of 3GPP TS 38.413 v16.0 may be referred.

PDU Session Resource Setup is described.

The purpose of the PDU Session Resource Setup procedure is to assign resources on Uu and NG-U for one or several PDU sessions and the corresponding QoS flows, and to setup corresponding DRBs for a given UE. The procedure uses UE-associated signalling.

The AMF initiates the procedure by sending a PDU SESSION RESOURCE SETUP REQUEST message to the NG-RAN node.

The PDU SESSION RESOURCE SETUP REQUEST message shall contain the information required by the NG-RAN node to setup the PDU session related NG-RAN configuration consisting of at least one PDU session resource and include each PDU session resource to setup in the PDU Session Resource Setup Request List IE.

Upon reception of the PDU SESSION RESOURCE SETUP REQUEST message, if resources are available for the requested configuration, the NG-RAN node shall execute the requested NG-RAN configuration and allocate associated resources over NG and over Uu for each PDU session listed in the PDU Session Resource Setup Request List IE.

PDU Session Resource Modify is described.

The purpose of the PDU Session Resource Modify procedure is to enable configuration modifications of already established PDU session(s) for a given UE. It is also to enable the setup, modification and release of the QoS flow for already established PDU session(s). The procedure uses UE-associated signalling.

The AMF initiates the procedure by sending a PDU SESSION RESOURCE MODIFY REQUEST message to the NG-RAN node.

The PDU SESSION RESOURCE MODIFY REQUEST message shall contain the information required by the NG-RAN node, which may trigger the NG-RAN configuration modification for the existing PDU sessions listed in the PDU Session Resource Modify Request List IE.

Upon reception of the PDU SESSION RESOURCE MODIFY REQUEST message, if the NG-RAN configuration is triggered to be modified and if resources are available for the modified NG-RAN configuration, the NG-RAN node shall execute the configuration modification for the requested PDU session.

Hereinafter, UE Context Setup and UE Context Modification (gNB-CU initiated) are described. Section 8.3 of 3GPP TS 38.473 v16.0 may be referred.

UE Context Setup is described.

The purpose of the UE Context Setup procedure is to establish the UE Context including, among others, SRB, and DRB configuration. The procedure uses UE-associated signalling.

The gNB-CU initiates the procedure by sending UE CONTEXT SETUP REQUEST message to the gNB-DU. If the gNB-DU succeeds to establish the UE context, it replies to the gNB-CU with UE CONTEXT SETUP RESPONSE. If no UE-associated logical F1-connection exists, the UE-associated logical F1-connection shall be established as part of the procedure.

The gNB-DU shall report to the gNB-CU, in the UE CONTEXT SETUP RESPONSE message, the result for all the requested DRBs and SRBs in the following way:

-   -   A list of DRBs which are successfully established shall be         included in the DRB Setup List IE;     -   A list of DRBs which failed to be established shall be included         in the DRB Failed to Setup List IE;     -   A list of SRBs which failed to be established shall be included         in the SRB Failed to Setup List IE.     -   A list of successfully established SRBs with logical channel         identities for primary path shall be included in the SRB Setup         List IE only if CA based PDCP duplication is initiated for the         concerned SRBs.

When the gNB-DU reports the unsuccessful establishment of a DRB or SRB, the cause value should be precise enough to enable the gNB-CU to know the reason for the unsuccessful establishment.

If the C-RNTIIE is included in the UE CONTEXT SETUP RESPONSE, the gNB-CU shall consider that the C-RNTI has been allocated by the gNB-DU for this UE context.

If the UE CONTEXT SETUP REQUEST message contains the RRC-Container IE, the gNB-DU shall send the corresponding RRC message to the UE via SRB1.

If the RAN UE ID IE is contained in the UE CONTEXT SETUP REQUEST message, the gNB-DU shall store and replace any previous information received.

UE Context Modification (gNB-CU initiated) is described.

The purpose of the UE Context Modification procedure is to modify the established UE Context, e.g., establishing, modifying and releasing radio resources. This procedure is also used to command the gNB-DU to stop data transmission for the UE for mobility. The procedure uses UE-associated signalling.

The UE CONTEXT MODIFICATION REQUEST message is initiated by the gNB-CU.

Upon reception of the UE CONTEXT MODIFICATION REQUEST message, the gNB-DU shall perform the modifications, and if successful reports the update in the UE CONTEXT MODIFICATION RESPONSE message.

The gNB-DU shall report to the gNB-CU, in the UE CONTEXT MODIFICATION

RESPONSE message, the result for all the requested or modified DRBs and SRBs in the following way:

-   -   A list of DRBs which are successfully established shall be         included in the DRB Setup List IE;     -   A list of DRBs which failed to be established shall be included         in the DRB Failed to be Setup List IE;     -   A list of DRBs which are successfully modified shall be included         in the DRB Modified List IE;     -   A list of DRBs which failed to be modified shall be included in         the DRB Failed to be Modified List IE;     -   A list of SRBs which failed to be established shall be included         in the SRB Failed to be Setup List IE.     -   A list of successfully established SRBs with logical channel         identities for primary path shall be included in the SRB Setup         List IE only if CA based PDCP duplication is initiated for the         concerned SRBs.     -   A list of successfully modified SRBs with logical channel         identities for primary path shall be included in the SRB         Modified List IE only if CA based PDCP duplication is initiated         for the concerned SRBs.

When the gNB-DU reports the unsuccessful establishment of a DRB or SRB, the cause value should be precise enough to enable the gNB-CU to know the reason for the unsuccessful establishment.

If the C-RNTI IE is included in the UE CONTEXT MODIFICATION RESPONSE, the gNB-CU shall consider that the C-RNTI has been allocated by the gNB-DU for this UE context.

If the UE CONTEXT MODIFICATION REQUEST message contains the RRC-Container IE, the gNB-DU shall send the corresponding RRC message to the UE. If the UE CONTEXT MODIFICATION REQUEST message includes the Execute Duplication IE, the gNB-DU shall perform CA based duplication, if configured, for the SRB for the included RRC-Container IE.

Hereinafter, gNB-CU-CP Configuration Update, Bearer Context Setup and Bearer Context Modification (gNB-CU-CP initiated) are described. Sections 8.2 and 8.3 of 3GPP TS 38.463 v16.0 may be referred.

gNB-CU-CP Configuration Update is described.

The purpose of the gNB-CU-CP Configuration Update procedure is to update application level configuration data needed for the gNB-CU-CP and the gNB-CU-UP to interoperate correctly on the E1 interface. This procedure does not affect existing UE-related contexts, if any. The procedure uses non-UE associated signalling.

The gNB-CU-CP initiates the procedure by sending a GNB-CU-CP CONFIGURATION UPDATE message to the gNB-CU-UP including an appropriate set of updated configuration data that it has just taken into operational use. The gNB-CU-UP responds with GNB-CU-CP CONFIGURATION UPDATE ACKNOWLEDGE message to acknowledge that it successfully updated the configuration data. If an information element is not included in the GNB-CU-CP CONFIGURATION UPDATE message, the gNB-CU-UP shall interpret that the corresponding configuration data is not changed and shall continue to operate with the existing related configuration data.

The updated configuration data shall be stored in both nodes and used as long as there is an operational TNL association or until any further update is performed.

Bearer Context Setup is described.

The purpose of the Bearer Context Setup procedure is to allow the gNB-CU-CP to establish a bearer context in the gNB-CU-UP. The procedure uses UE-associated signalling.

The gNB-CU-CP initiates the procedure by sending the BEARER CONTEXT SETUP REQUEST message to the gNB-CU-UP. If the gNB-CU-UP succeeds to establish the requested resources, it replies to the gNB-CU-CP with the BEARER CONTEXT SETUP RESPONSE message.

The gNB-CU-UP shall report to the gNB-CU-CP, in the BEARER CONTEXT SETUP RESPONSE message, the result for all the requested resources in the following way:

For E-UTRAN:

-   -   A list of DRBs which are successfully established shall be         included in the DRB Setup List IE;     -   A list of DRBs which failed to be established shall be included         in the DRB Failed List IE;

For NG-RAN:

-   -   A list of PDU Session Resources which are successfully         established shall be included in the PDU Session Resource Setup         List IE;     -   A list of PDU Session Resources which failed to be established         shall be included in the PDU Session Resource Failed List IE;     -   For each established PDU Session Resource, a list of DRBs which         are successfully established shall be included in the DRB Setup         List IE;     -   For each established PDU Session Resource, a list of DRBs which         failed to be established shall be included in the DRB Failed         List IE;     -   For each established DRB, a list of QoS Flows which are         successfully established shall be included in the Flow Setup         List IE;     -   For each established DRB, a list of QoS Flows which failed to be         established shall be included in the Flow Failed List IE;

When the gNB-CU-UP reports the unsuccessful establishment of a PDU Session Resource, DRB or QoS Flow the cause value should be precise enough to enable the gNB-CU-CP to know the reason for the unsuccessful establishment.

Bearer Context Modification (gNB-CU-CP initiated) is described.

The purpose of the Bearer Context Modification procedure is to allow the gNB-CU-CP to modify a bearer context in the gNB-CU-UP. The procedure uses UE-associated signalling.

The gNB-CU-CP initiates the procedure by sending the BEARER CONTEXT MODIFICATION REQUEST message to the gNB-CU-UP. If the gNB-CU-UP succeeds to modify the bearer context, it replies to the gNB-CU-CP with the BEARER CONTEXT MODIFICATION RESPONSE message.

The gNB-CU-UP shall report to the gNB-CU-CP, in the BEARER CONTEXT MODIFICATION RESPONSE message, the result for all the requested resources in the following way:

For E-UTRAN:

-   -   A list of DRBs which are successfully established shall be         included in the DRB Setup List IE;     -   A list of DRBs which failed to be established shall be included         in the DRB Failed List IE;     -   A list of DRBs which are successfully modified shall be included         in the DRB Modified List IE;     -   A list of DRBs which failed to be modified shall be included in         the DRB Failed To Modify List IE;

For NG-RAN:

-   -   A list of PDU Session Resources which are successfully         established shall be included in the PDU Session Resource Setup         List IE;     -   A list of PDU Session Resources which failed to be established         shall be included in the PDU Session Resource Failed List IE;     -   A list of PDU Session Resources which are successfully modified         shall be included in the PDU Session Resource Modified List IE;     -   A list of PDU Session Resources which failed to be modified         shall be included in the PDU Session Resource Failed To Modify         List IE;     -   For each successfully established or modified PDU Session         Resource, a list of DRBs which are successfully established         shall be included in the DRB Setup List IE;     -   For each successfully established or modified PDU Session         Resource, a list of DRBs which failed to be established shall be         included in the DRB Failed List IE;     -   For each successfully modified PDU Session Resource, a list of         DRBs which are successfully modified shall be included in the         DRB Modified List IE;     -   For each successfully modified PDU Session Resource, a list of         DRBs which failed to be modified shall be included in the DRB         Failed To Modify List IE;     -   For each successfully established or modified DRB, a list of QoS         Flows which are successfully established shall be included in         the Flow Setup List IE;     -   For each successfully established or modified DRB, a list of QoS         Flows which failed to be established shall be included in the         Flow Failed List IE;

When the gNB-CU-UP reports the unsuccessful establishment of a PDU Session Resource, DRB or QoS Flow the cause value should be precise enough to enable the gNB-CU-CP to know the reason for the unsuccessful establishment.

Meanwhile, in NR, Multicast and Broadcast Services (MBS) may be supported. For example, the MBS may be provided for wireless devices in RRC_CONNECTED state.

A wireless device may receive MBS via multicast transmission or unicast transmission from a network. For example, multicast transmission may be referred as a point to multipoint (PTM) transmission, and unicast transmission may be referred as point to point (PTP) transmission.

A network may need to perform dynamic change of MBS delivery between multicast transmission and unicast transmission with service continuity for a wireless device in a connected state. For example, if the service continuity for a wireless device during the change is not guaranteed, user experience may be degraded.

Therefore, studies for switching of multicast and broadcast service between multicast and unicast in a wireless communication system are needed.

Hereinafter, a method for switching of multicast and broadcast service between multicast and unicast in a wireless communication system, according to some embodiments of the present disclosure, will be described.

FIG. 9 shows an example of a method for switching of multicast and broadcast service between multicast and unicast in a wireless communication system.

In particular, FIG. 9 shows an example of a method performed by a Central Unit (CU)-Control Plane (CP) of a Radio Access Network (RAN) node in a wireless communication system.

For example, the RAN node may be connected to a core network node in the wireless communication system. For example, the RAN node may include a CU-User Plane (UP) connected to the CU-CP. For example, the RAN node may include a Distributed Unit (DU) connected to the CU-CP. For example, the CU-UP may be connected to the DU.

In step S901, the CU-CP may establish a connection with a wireless device for a Multicast and/or Broadcast Service (MBS).

For example, the CU-CP may receive, from a core network node (for example, an Access and Mobility Management Function (AMF)), a Packet Data Unit (PDU) Session Resource Setup Request message or a PDU Session Resource Modify Request message to establish or modify a PDU session or setup QoS flow for the MBS.

The Packet Data Unit (PDU) Session Resource Setup Request message or the PDU Session Resource Modify Request message may include MBS Information, for example, service identity, MBS tunnel endpoint ID (TEID), multicast address, and/or MBS flow identity. For example, the MBS information may indicate the MBS provided through the PDU session or QoS flow to be established.

For example, the CU-CP may transmit, to the CU-UP, a Bearer Context Setup Request message or a Bearer Context Modification Request message in order to request establishing the bearer (for example, data radio bearer or unicast bearer) between the CU-UP and the DU for the MBS.

The Bearer Context Setup Request or the Bearer Context Modification Request message may include an ID of the MBS to indicate that the requested bearer is related to which MBS. For example, the ID of the MBS may include a service identity and/or an MBS flow identity.

For example, the CU-CP may receive, from the CU-UP, a Bearer Context Setup Response or a Bearer Context Modification Response message in response to the Bearer Context Setup Request or the Bearer Context Modification Request message.

For example, the CU-CP may transmit, to the DU, a UE Context Setup Request or a UE Context Modification Request in order to setup bearer (for example, data radio bearer or unicast bearer) between the DU and a wireless device for the MBS.

The UE Context Setup Request or the UE Context Modification Request may contain the ID of the MBS to indicate that the requested bearer is related to which MBS.

For example, the CU-CP may receive, from the DU, a UE Context Setup Response or a UE Context Modification Response message including configuration for the requested bearer.

For example, the CU-CP may transmit, to the CU-UP, a Bearer Context Modification Request message including the ID of the MBS.

For example, the CU-CP may receive, from the CU-UP, a Bearer Context Modification Response message in response to the Bearer Context Modification Request message.

For example, the CU-CP may transmit, to the DU, a DL RRC Message Transfer message including an RRCReconfiguration with the configuration of bearer (for example, data radio bearer or unicast bearer) for the MBS.

For example, the CU-CP may receive, from the DU, an UL RRC Message Transfer message to forward an RRCReconfigurationComplete received from the wireless device.

For example, the CU-CP may transmit, to the core network node, a PDU Session Resource Setup Response or a PDU Session Resource Modify Response message.

The PDU Session Resource Setup Response or the PDU Session Resource Modify Response message may include the MBS information to indicate the MBS which the core network node requests. For example, the MBS information may include service identity, MBS TEID (downlink), and/or MBS flow identity.

In step S902, the CU-CP may provide, via a CU-UP of the RAN node, the MBS by using a first transmission to the wireless device.

For example, the first transmission may be one of unicast transmission or multicast transmission.

In step S903, the CU-CP may receive, from the CU-UP, a message including a retransmission information on data transmission related to the MBS.

For example, the first message may include an identity (ID) of the MBS.

For example, the first message may be a Multicast Data Notification message or a new message indicating the situation for the MBS.

For example, the CU-CP may provide, to plurality of wireless devices, plurality of MBS using plurality of bearers. The retransmission information includes at least one of (1) a retransmission rate per wireless device receiving the MBS, (2) a retransmission rate per bearer for the MBS, and/or (3) a retransmission rate per MBS.

For example, the first message may be transmitted from the CU-UP periodically. For example, the first message may be transmitted from the CU-UP based on that a certain condition is met.

In step S904, the CU-CP may determine whether to perform a switch of the first transmission to a second transmission for the MBS based on the retransmission information.

For example, the second transmission may be one of unicast transmission or multicast transmission, which is different from the first transmission.

According to some embodiments of the present disclosure, the CU-CP may determine to perform the switch from the first transmission to the second transmission.

In this case, for example, the CU-CP may transmit, to the CU-UP, a second message to request the switch of the first transmission to the second transmission for the MBS. For example, the second message may be a Transmission Type Change Request message or a new message.

For example, the the second message may include an ID of the MBS and/or an ID of the wireless device.

For example, the second message may include (1) multicast radio bearer (MRB) setup list including at least one MRB ID for the MBS, (2) Service Data Adaptation Protocol (SDAP) configuration for the MBS, (3) Packet Data Convergence Protocol (PDCP) configurations for the MBS, and/or (4) Quality of service (QoS) flow for the MBS.

For example, the third message may be a Transmission Type Change Response message or a new message.

For example, the CU-CP may receive, from the CU-UP, a third message informing establishment of radio resources for the MBS. For example, the third message may be transmitted from the CU-UP when allocation of the requested MRB resources for the MBS is available.

For example, the third message may include (1) an ID of the MBS and/or (2) an MRB Setup List to inform established MRB resources for the MBS.

For example, the CU-CP may transmit, to a Distributed Unit (DU) of the RAN node, a fourth message to request the switch of the first transmission to the second transmission for the MBS. For example, the fourth message may include an ID of the MBS.

For example, the fourth message may be a Transmission Switching Request message or a new message.

For example, the CU-CP may receive, from the DU, a fifth message informing that allocating radio resource for the second transmission is available.

For example, the fifth message may be a Transmission Switching Response message or a new message.

For example, the fifth message may include (1) channel information for the MBS, (2) the ID of the MBS, and/or (3) a downlink tunnel endpoint ID (DL TEID) for the MBS from the CU-UP to the DU.

For example, the CU-CP may transmit, to the CU-UP, a sixth message including (1) the ID of the MBS, and/or (2) the DL TEID.

For example, the sixth message may be a CU-CP Configuration Update message or a new message.

In step S905, the CU-CP may provide, via the CU-UP, the MBS by using the second transmission to the wireless device,

According to some embodiments of the present disclosure, a network (for example, a base station) may support RAN basic functions for broadcast/multicast for UEs in RRC_CONNECTED state.

For example, a network may support a group scheduling mechanism to allow UEs to receive Broadcast/Multicast service. For example, a network may support necessary enhancements that are required to enable simultaneous operation with unicast reception.

For example, a network may support for dynamic change of Broadcast/Multicast service delivery between multicast (PTM) and unicast (PTP) with service continuity for a given UE.

For example, a network may support for basic mobility with service continuity.

For example, a network may assume that the necessary coordination function (like functions hosted by MCE) resides in the gNB-CU. For example, a network may support required changes on the RAN architecture and interfaces, considering the results of the SA2 SI on Broadcast/Multicast.

For example, a network may support required changes to improve reliability of Broadcast/Multicast service, for example, by UL feedback. The level of reliability may be based on the requirements of the application/service provided.

For example, a network may support for dynamic control of the Broadcast/Multicast transmission area within one gNB-DU and specify what is needed to enable it.

According to some embodiments of the present disclosure, a network (for example, a base station) may support RAN basic functions for broadcast/multicast for UEs in RRC_IDLE/RRC INACTIVE states.

According to some embodiments of the present disclosure, a network (for example, a base station) may support required changes to enable the reception of Point to Multipoint transmissions by UEs in RRC_IDLE/RRC_INACTIVE states, with the aim of keeping maximum commonality between RRC_CONNECTED state and RRC_IDLE/RRC_INACTIVE state for the configuration of PTM reception.

The possibility of receiving Point to Multipoint transmissions by UEs in RRC_IDLE/RRC_INACTIVE states, without the need for those UEs to get the configuration of the PTM bearer carrying the Broadcast/Multicast service while in RRC CONNECTED state beforehand, may be supported by the network to verification of service subscription and authorization assumptions.

According to some embodiments of the present disclosure, a network (for example, a base station) may support a high level MBS architecture, with the further restriction that only NR in NG-RAN (for example, connected to 5GC) is considered as RAT.

For example, a network may provide Multicast/Broadcast transmissions in FR2.

For example, a network may support flexible resource allocation between Unicast and Broadcast/Multicast services.

Hereinafter, a method for determining to switch between unicast and multicast performed by a gNB-DU and a gNB-CU in a wireless communication system, according to some embodiments of the present disclosure, will be described.

For example, the gNB-CU may request the switching between multicast and unicast for the multicast and/or broadcast service (MBS) to the gNB-DU based on the measurement information for the bearer(s) related to the MBS, which is provided by the UE. The gNB-DU may respond acceptance for the request of the gNB-CU considering the current radio situation.

For example, in case of unicast to multicast switching, the gNB-DU may provide the gNB-CU with the multicast channel information for the MBS in order to offer this information to the UE(s) provided with the MBS.

Also, the gNB-CU may provide the gNB-DU with the MBS identity (for example, service identity, and/or MBS flow identity), when the AMF requests establishing PDU session or QoS flow for the MBS.

Hereinafter, a method for switching of multicast and broadcast service between multicast and unicast performed by a gNB-CU-CP, a gNB-CU-UP, and a gNB-DU in a wireless communication system, according to some embodiments of the present disclosure, will be described.

For example, the gNB-CU-CP may request the switching between multicast and unicast for the multicast/broadcast service (MBS) to the gNB-CU-UP and the gNB-DU based on the information on retransmission rate for multicast/broadcast data transmission related to the MBS, which is provided by the gNB-CU-UP. The gNB-CU-UP and the gNB-DU may respond acceptance for the request of the gNB-CU-CP considering their respective resource situation.

For example, in case of unicast to multicast switching, the gNB-CU-UP and the gNB-DU may provide the gNB-CU-CP with a setup list of multicast radio bearer (MRB) for the MBS and the multicast/broadcast channel information for the MBS in order to offer this information to the UE(s) provided with the MBS respectively.

For example, in case of multicast to unicast switching, the gNB-CU-UP and the gNB-DU may remove the allocated resource for MRB related to the MBS based on a remove list of MRB provided by the gNB-CU-CP.

For example, the gNB-CU-CP may provide the gNB-CU-UP and the gNB-DU with the MBS identity (for example, service identity, and/or MBS flow identity) when the AMF requests establishing PDU session or QoS flow for the MBS.

FIGS. 10A, 10B, 10C, and 10D show an example of a procedure for switching of multicast and broadcast service between multicast and unicast in a wireless communication system, according to some embodiments of the present disclosure.

In steps S1001 to S1020, a procedure for switching from unicast to multicast may be performed.

In step S1001, the AMF may send the PDU Session Resource Setup Request or the PDU Session Resource Modify Request message to the gNB-CU-CP in order to establish the PDU session or setup QoS flow for multicast/broadcast data transmission. This message may include the MBS Information, for example, service identity, MBS TEID, multicast address, and/or MBS flow identity, to indicate the MBS provided through the PDU session or QoS flow to be established.

In step S1002, on receiving the setup or modify request message, the gNB-CU-CP may store the received MBS related information. The gNB-CU-CP may transmit the Bearer Context Setup/Modification Request message to the gNB-CU-UP in order to request establishing the bearer (for example, data radio bearer or unicast bearer) for multicast/broadcast data transmission between the gNB-CU-UP and the gNB-DU. This message may include the MBS Identity, for example, service identity and/or MBS flow identity, to indicate that the requested bearer is related to which MBS.

In step S1003, upon the receipt of the setup or modification request message, the gNB-CU-UP may send the Bearer Context Setup Response or the Bearer Context Modification Response message to the gNB-CU-CP.

In step S1004, on receiving the setup or modification response message from the gNB-CU-UP, the gNB-CU-CP may transmit the UE Context Setup Request or the UE Context Modification Request to the gNB-DU in order to request the setup of bearer (for example, data radio bearer or unicast bearer) for multicast/broadcast data transmission between the gNB-DU and the UE. This message may contain the MBS Identity (for example, service identity and/or MBS flow identity) to indicate that the requested bearer is related to which MBS.

In step S1005, when to receive the setup or modification request message, the gNB-DU can identify the MBS to be provided to the UE through the request bearer. Also, the gNB-DU may know the number of UEs provided with the MBS or interested in the MBS. Including the configuration for requested bearer, the gNB-DU may respond with the UE Context Setup Response or the UE Context Modification Response message to the gNB-CU-CP.

In step S1006, upon the receipt of the message from the gNB-DU, the gNB-CU-CP may send the Bearer Context Modification Request message to the gNB-CU-UP. This message may contain the MBS Identity to indicate that the requested bearer is related to which MBS.

In step S1007, on receiving the message from the gNB-CU-CP, the gNB-CU-UP may respond with the Bearer Context Modification Response message.

In step S1008, the gNB-CU-CP may send the DL RRC Message Transfer message containing the RRCReconfiguration with the configuration of bearer (for example, data radio bearer or unicast bearer) for multicast/broadcast data transmission to the gNB-DU.

In step S1009, the gNB-DU may transmit the UL RRC Message Transfer message to the gNB-CU-CP to forward the RRCReconfigurationComplete received from the UE.

In step S1010, when to receive the message from the gNB-DU, the gNB-CU-CP may send to the AMF the PDU Session Resource Setup Response or the PDU Session Resource Modify Response message. This message may include the MBS Information (for example, service identity, MBS TEID (downlink), and/or MBS flow identity) to indicate the MBS which the AMF requests.

In step S1011, the gNB-CU-UP may transmit the Multicast Data Notification, existing, or new message to the gNB-CU-CP to indicate the situation for multicast data transmission toward the UE via the established bearer(s). This message may contain the MBS Identity to indicate that the situation for multicast data transmission is related to the MBS. This message may include the Retransmission Information with the retransmission rate per UE provided with the MBS, per bearer for the MBS, and/or per MBS. This message may be sent periodically or when the certain condition is met.

In step S1012, based on the message received from the gNB-CU-UP, the gNB-CU-CP may determine whether to perform switching from unicast to multicast.

In step S1013, the gNB-CU-CP may send the Transmission Type Change Request, existing, or new message to the gNB-CU-UP to request the change from unicast to multicast. This message may include the MBS Identity to indicate the MBS to be changed. Also, this message may contain the UE ID (for example, gNB-CU-CP/gNB-CU-UP UE E1AP ID) to indicate removing the established bearer(s) (for example, data radio bearer or unicast bearer) for multicast/broadcast data transmission related to the MBS which an indicated UE(s) has used. In addition, this message may include the multicast radio bearer (MRB) Setup List with the MRB ID, the SDAP/PDCP configurations, and/or the QoS flow related information in order to request setup of MRB for the indicated MBS.

In step S1014, when to receive the message from the gNB-CU-CP, the gNB-CU-UP may check whether to be able to allocate the requested MRB resources for the MBS. If available, the gNB-CU-UP may respond with the Transmission Type Change Response, existing, or new message to the gNB-CU-CP. This message may contain the MBS Identity and MRB Setup List to indicate establishing the MRB resources for the indicated MBS.

Although the request message from the gNB-CU-CP does not include the UE ID, based on the received MBS Identity, the gNB-CU-UP may remove the established bearer(s) (for example, data radio bearer or unicast bearer) for multicast/broadcast data transmission related to the MBS.

In step S1015, in order to request the switching from unicast to multicast, the gNB-CU-CP may send the Transmission Switching Request, existing, or new message to the gNB-DU. This message may include the MBS Identity to indicate the MBS to be switched. In addition, this message may contain the Switching Indication to inform the gNB-DU of the unicast to multicast switching. This indication may be MRB Setup List with the MRB ID, and/or the QoS flow related information.

In addition, this message may contain the UE ID (for example, gNB-CU/gNB-DU UE F1AP ID) to indicate removing the established bearer(s) (for example, data radio bearer or unicast bearer) for multicast/broadcast data transmission related to the MBS which an indicated UE(s) has used.

In step S1016, on receiving the message from the gNB-CU-CP, the gNB-DU may check whether to be able to allocate the radio resource for MRB related to the indicated MBS. If available, it responds with the Transmission Switching Response, existing, or new message to the gNB-CU-CP. This message may include the MBS Channel Information and the MBS Identity to provide multicast channel information to the UE(s) provided with the indicated MBS.

Although the request message from the gNB-CU-CP does not include the UE ID, based on the received MBS Identity, the gNB-DU may remove the established bearer(s) (for example, data radio bearer or unicast bearer) for multicast/broadcast data transmission related to the MBS. In addition, this message may include the downlink tunnel endpoint (DL TEID) for multicast/broadcast data transmission from the gNB-CU-UP to the gNB-DU.

In step S1017, upon the receipt of the message from the gNB-DU, the gNB-CU-CP may send the gNB-CU-CP Configuration Update or new message with the DL TEID to the gNB-CU-UP in order to indicate downlink tunnel endpoint to be used for multicast/broadcast data transmission from the gNB-CU-UP to the gNB-DU. This message may contain the MBS Identity to indicate that the requested bearer is related to which MBS.

In step S1018, on receiving the message from the gNB-CU-CP, the gNB-CU-UP may store the received DL TEID and use the received DL TEID to transmit multicast/broadcast data for the indicated MBS. The gNB-CU-UP may respond with the gNB-CU-CP Configuration Update Acknowledge or new message.

In step S1019, when to receive the message from the gNB-CU-UP, the gNB-CU-CP may transmit the DL RRC Message Transfer message with the RRCReconfiguration in order to provide the multicast channel related information to the UE provided with the indicated MBS.

If there are multiple UEs provided with the indicated MBS, the gNB-CU may send this F1AP message with the RRCReconfiguration to all of those UEs.

In step S1020, the gNB-DU may send the UL RRC Message Transfer message to the gNB-CU-CP to forward the RRCReconfigurationComplete received from the UE.

In steps S1021 to S1034, a procedure for switching from multicast to unicast may be performed.

In step S1021, the gNB-CU-UP may transmit the Multicast Data Notification, existing, or new message to the gNB-CU-CP to indicate the situation for multicast data transmission toward the UE via the switched/changed bearer(s). This message may contain the MBS Identity to indicate that the situation for multicast data transmission is related to the MBS. This message may include the Retransmission Information with the retransmission rate per UE provided with the MBS, per bearer for the MBS, and/or per MBS. This message may be sent periodically or when the certain condition is met.

In step S1022, based on the message received from the gNB-CU-UP, the gNB-CU-CP may determine whether to perform switching from multicast to unicast.

In step S1023, the gNB-CU-CP may send the Bearer Context Modification Request message to the gNB-CU-UP to request establishing the bearer (for example, data radio bearer or unicast bearer) for multicast/broadcast data transmission between the gNB-CU-UP and the gNB-DU. This message may include the MBS Identity to indicate that the requested bearer is related to which MBS.

In step S1024, upon the receipt of the modification request message, the gNB-CU-UP may transmit the Bearer Context Modification Response message to the gNB-CU-CP.

In step S1025, on receiving the modification response message from the gNB-CU-UP, the gNB-CU-CP may send the UE Context Modification Request to the gNB-DU in order to request the setup of bearer (for example, data radio bearer or unicast bearer) for multicast/broadcast data transmission between the gNB-DU and the UE. This message may contain the MBS Identity to indicate that the requested bearer is related to which MBS.

In step S1026, when to receive the modification request message, the gNB-DU may respond with the UE Context Modification Response message including the configuration for requested bearer to the gNB-CU-CP.

In step S1027, upon the receipt of the message from the gNB-DU, the gNB-CU-CP may transmit the Bearer Context Modification Request message to the gNB-CU-UP. This message may contain the MBS Identity to indicate that the requested bearer is related to which MBS.

In step S1028, on receiving the message from the gNB-CU-CP, the gNB-CU-UP may respond with the Bearer Context Modification Response message.

For step S1023 to S1028, if there are multiple UEs provided with the same MBS, these steps may be performed for each of that UE before step S1029 is proceeded.

In step S1029, when to receive the message from the gNB-CU-UP, the gNB-CU-CP may send the Transmission Type Change Request, existing, or new message to the gNB-CU-UP to request the change from multicast to unicast. This message may include the MBS Identity to indicate the MBS to be changed. In addition, this message may include the MRB Remove List with the MRB ID in order to request removal of MRB for the indicated MBS.

In step S1030, when to receive the message from the gNB-CU-CP, based on the received information, the gNB-CU-UP may remove the allocated resources for MRB related to the indicated MBS. The gNB-CU-UP may respond with the Transmission Type Change Response, existing, or new message to the gNB-CU-CP. This message may contain the MBS Identity to indicate the MBS to be changed from multicast to unicast.

In step S1031, in order to request the switching from multicast to unicast, the gNB-CU-CP may send the Transmission Switching Request, existing, or new message to the gNB-DU. This message may include the MBS Identity to indicate the MBS to be switched. In addition, this message may contain the Switching Indication to inform the gNB-DU of the multicast to unicast switching. This indication may be the MRB Remove List with the MRB ID.

In step S1032, on receiving the message from the gNB-CU-CP, based on the received information, the gNB-DU may remove the allocated radio resource for MRB related to the indicated MBS. The gNB-DU may respond with the Transmission Switching Response, existing, or new message to the gNB-CU-CP. This message may include the MBS Identity to indicate the MBS to be switched from multicast to unicast.

In step S1033, when to receive the message from the gNB-DU, the gNB-CU-CP may transmit the DL RRC Message Transfer message containing the RRCReconfiguration with the configuration of bearer (for example, data radio bearer or unicast bearer) for multicast/broadcast data transmission to the gNB-DU.

In step S1034, the gNB-DU may send the UL RRC Message Transfer message to the gNB-CU-CP to forward the RRCReconfigurationComplete received from the UE.

Hereinafter, an apparatus for switching of multicast and broadcast service between multicast and unicast in a wireless communication system, according to some embodiments of the present disclosure, will be described.

For example, a Central Unit (CU)-Control Plane (CP) of a Radio Access Network (RAN) node may include a processor, and a memory.

According to some embodiments of the present disclosure, the processor may be configured to be coupled operably with the memory.

The processor may be configured to establish a connection with a wireless device for a Multicast and/or Broadcast Service (MBS). The processor may be configured to providing, via a CU-User Plane (UP) of the RAN node, the MBS by using a first transmission to the wireless device. The processor may be configured to receive, from the CU-UP, a first message including a retransmission information on data transmission related to the MBS. The processor may be configured to determine whether to perform a switch of the first transmission to a second transmission for the MBS based on the retransmission information. The processor may be configured to provide, via the CU-UP, the MBS by using the second transmission to the wireless device. The first transmission is one of unicast transmission or multicast transmission, and the second transmission is another one of unicast transmission or multicast transmission.

For example, the first message may include an identity (ID) of the MBS.

For example, the retransmission information may include a retransmission rate per wireless device receiving the MBS.

For example, the retransmission information may include a retransmission rate per bearer for the MBS.

For example, the retransmission information may include a retransmission rate per MBS.

For example, the first message may be transmitted from the CU-UP periodically.

For example, the first message may be transmitted from the CU-UP based on that a certain condition is met.

According to some embodiments of the present disclosure, the processor may be configured to transmit, to the CU-UP, a second message to request the switch of the first transmission to the second transmission for the MBS.

For example, the second message may include an ID of the MBS and/or an ID of the wireless device.

For example, the second message may include (1) multicast radio bearer (MRB) setup list including at least one MRB ID for the MBS, (2) Service Data Adaptation Protocol (SDAP) configuration for the MBS, (3) Packet Data Convergence Protocol (PDCP) configurations for the MBS, and/or (4) Quality of service (QoS) flow for the MBS.

According to some embodiments of the present disclosure, the processor may be configured to receive, from the CU-UP, a third message informing establishment of radio resources for the MBS.

For example, the third message may include (1) an ID of the MBS and/or (2) an MRB Setup List to inform established MRB resources for the MBS.

According to some embodiments of the present disclosure, the processor may be configured to transmit, to a Distributed Unit (DU) of the RAN node, a fourth message to request the switch of the first transmission to the second transmission for the MBS.

For example, the fourth message may include an ID of the MBS.

For example, the processor may be configured to receive, from the DU, a fifth message informing that allocating radio resource for the second transmission is available. For example, the fifth message may include (1) channel information for the MBS, (2) the ID of the MBS, and/or (3) a downlink tunnel endpoint ID (DL TEID) for the MBS from the CU-UP to the DU.

For example, the processor may be configured to transmit, to the CU-UP, a sixth message including (1) the ID of the MBS, and/or (2) the DL TEID.

For example, referring to FIG. 7 , a gNB-CU could be an example of the CU of a RAN node for determining to switch between unicast and multicast.

Hereinafter, a processor for a Central Unit (CU) for switching of multicast and broadcast service between multicast and unicast in a wireless communication system, according to some embodiments of the present disclosure, will be described.

The processor may be configured to control the CU to establish a connection with a wireless device for a Multicast and/or Broadcast Service (MBS). The processor may be configured to control the CU to providing, via a CU-User Plane (UP) of the RAN node, the MBS by using a first transmission to the wireless device. The processor may be configured to control the CU to receive, from the CU-UP, a first message including a retransmission information on data transmission related to the MBS. The processor may be configured to control the CU to determine whether to perform a switch of the first transmission to a second transmission for the MBS based on the retransmission information. The processor may be configured to control the CU to provide, via the CU-UP, the MBS by using the second transmission to the wireless device. The first transmission is one of unicast transmission or multicast transmission, and the second transmission is another one of unicast transmission or multicast transmission.

For example, the first message may include an identity (ID) of the MBS.

For example, the retransmission information may include a retransmission rate per wireless device receiving the MBS.

For example, the retransmission information may include a retransmission rate per bearer for the MBS.

For example, the retransmission information may include a retransmission rate per MBS.

For example, the first message may be transmitted from the CU-UP periodically.

For example, the first message may be transmitted from the CU-UP based on that a certain condition is met.

According to some embodiments of the present disclosure, the processor may be configured to control the CU to transmit, to the CU-UP, a second message to request the switch of the first transmission to the second transmission for the MBS.

For example, the second message may include an ID of the MBS and/or an ID of the wireless device.

For example, the second message may include (1) multicast radio bearer (MRB) setup list including at least one MRB ID for the MBS, (2) Service Data Adaptation Protocol (SDAP) configuration for the MBS, (3) Packet Data Convergence Protocol (PDCP) configurations for the MBS, and/or (4) Quality of service (QoS) flow for the MBS.

According to some embodiments of the present disclosure, the processor may be configured to control the CU to receive, from the CU-UP, a third message informing establishment of radio resources for the MBS.

For example, the third message may include (1) an ID of the MBS and/or (2) an MRB Setup List to inform established MRB resources for the MBS.

According to some embodiments of the present disclosure, the processor may be configured to control the CU to transmit, to a Distributed Unit (DU) of the RAN node, a fourth message to request the switch of the first transmission to the second transmission for the MBS.

For example, the fourth message may include an ID of the MBS.

For example, the processor may be configured to control the CU to receive, from the DU, a fifth message informing that allocating radio resource for the second transmission is available. For example, the fifth message may include (1) channel information for the MBS, (2) the ID of the MBS, and/or (3) a downlink tunnel endpoint ID (DL TEID) for the MBS from the CU-UP to the DU.

For example, the processor may be configured to control the CU to transmit, to the CU-UP, a sixth message including (1) the ID of the MBS, and/or (2) the DL TEID.

Hereinafter, a non-transitory computer-readable medium has stored thereon a plurality of instructions for switching of multicast and broadcast service between multicast and unicast in a wireless communication system, according to some embodiments of the present disclosure, will be described.

According to some embodiment of the present disclosure, the technical features of the present disclosure could be embodied directly in hardware, in a software executed by a processor, or in a combination of the two. For example, a method performed by a wireless device in a wireless communication may be implemented in hardware, software, firmware, or any combination thereof. For example, a software may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other storage medium.

Some example of storage medium is coupled to the processor such that the processor can read information from the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. For other example, the processor and the storage medium may reside as discrete components.

The computer-readable medium may include a tangible and non-transitory computer-readable storage medium.

For example, non-transitory computer-readable media may include random access memory (RAM) such as synchronous dynamic random access memory (SDRAM), read-only memory (ROM), non-volatile random access memory (NVRAM), electrically erasable programmable read-only memory (EEPROM), FLASH memory, magnetic or optical data storage media, or any other medium that can be used to store instructions or data structures. Non-transitory computer-readable media may also include combinations of the above.

In addition, the method described herein may be realized at least in part by a computer-readable communication medium that carries or communicates code in the form of instructions or data structures and that can be accessed, read, and/or executed by a computer.

According to some embodiment of the present disclosure, a non-transitory computer-readable medium has stored thereon a plurality of instructions. The stored a plurality of instructions may be executed by a processor of a Central Unit (CU).

The stored a plurality of instructions may cause the CU to establish a connection with a wireless device for a Multicast and/or Broadcast Service (MBS). The stored a plurality of instructions may cause the CU to providing, via a CU-User Plane (UP) of the RAN node, the MBS by using a first transmission to the wireless device. The stored a plurality of instructions may cause the CU to receive, from the CU-UP, a first message including a retransmission information on data transmission related to the MBS. The stored a plurality of instructions may cause the CU to determine whether to perform a switch of the first transmission to a second transmission for the MBS based on the retransmission information. The stored a plurality of instructions may cause the CU to provide, via the CU-UP, the MBS by using the second transmission to the wireless device. The first transmission is one of unicast transmission or multicast transmission, and the second transmission is another one of unicast transmission or multicast transmission.

For example, the first message may include an identity (ID) of the MBS.

For example, the retransmission information may include a retransmission rate per wireless device receiving the MBS.

For example, the retransmission information may include a retransmission rate per bearer for the MBS.

For example, the retransmission information may include a retransmission rate per MBS.

For example, the first message may be transmitted from the CU-UP periodically.

For example, the first message may be transmitted from the CU-UP based on that a certain condition is met.

According to some embodiments of the present disclosure, the stored a plurality of instructions may cause the CU to transmit, to the CU-UP, a second message to request the switch of the first transmission to the second transmission for the MBS.

For example, the second message may include an ID of the MBS and/or an ID of the wireless device.

For example, the second message may include (1) multicast radio bearer (MRB) setup list including at least one MRB ID for the MBS, (2) Service Data Adaptation Protocol (SDAP) configuration for the MBS, (3) Packet Data Convergence Protocol (PDCP) configurations for the MBS, and/or (4) Quality of service (QoS) flow for the MBS.

According to some embodiments of the present disclosure, the stored a plurality of instructions may cause the CU to receive, from the CU-UP, a third message informing establishment of radio resources for the MBS.

For example, the third message may include (1) an ID of the MBS and/or (2) an MRB Setup List to inform established MRB resources for the MBS.

According to some embodiments of the present disclosure, the stored a plurality of instructions may cause the CU to transmit, to a Distributed Unit (DU) of the RAN node, a fourth message to request the switch of the first transmission to the second transmission for the MBS.

For example, the fourth message may include an ID of the MBS.

For example, the stored a plurality of instructions may cause the CU to receive, from the DU, a fifth message informing that allocating radio resource for the second transmission is available. For example, the fifth message may include (1) channel information for the MBS, (2) the ID of the MBS, and/or (3) a downlink tunnel endpoint ID (DL TEID) for the MBS from the CU-UP to the DU.

For example, the stored a plurality of instructions may cause the CU to transmit, to the CU-UP, a sixth message including (1) the ID of the MBS, and/or (2) the DL TEID.

The present disclosure may have various advantageous effects.

According to some embodiments of the present disclosure, a Radio Access Network (RAN) node (for example, a base station such as an eNB or a gNB) could efficiently perform switching of multicast and broadcast service between multicast and unicast.

For example, a RAN node could efficiently determine to switch between unicast and multicast for the MBS based on radio situation of the gNB-CU-UP.

For example, a gNB-central unit (CU)-Control Plane (CP), a gNB-CU-User Plane (UP), and a gNB-distributed unit (DU) could perform the switching between unicast and multicast for the MBS efficiently.

Therefore, the RAN node could use the radio resource for multicast and/or broadcast efficiently. In addition, a wireless communication system could avoid the degradation of user experience by switching of multicast and broadcast service between multicast and unicast efficiently.

According to some embodiments of the present disclosure, a wireless communication system could provide an efficient solution for switching of multicast and broadcast service between multicast and unicast by considering radio situation of the gNB-CU-UP.

Advantageous effects which can be obtained through specific embodiments of the present disclosure are not limited to the advantageous effects listed above. For example, there may be a variety of technical effects that a person having ordinary skill in the related art can understand and/or derive from the present disclosure. Accordingly, the specific effects of the present disclosure are not limited to those explicitly described herein, but may include various effects that may be understood or derived from the technical features of the present disclosure.

Claims in the present disclosure can be combined in a various way. For instance, technical features in method claims of the present disclosure can be combined to be implemented or performed in an apparatus, and technical features in apparatus claims can be combined to be implemented or performed in a method. Further, technical features in method claim(s) and apparatus claim(s) can be combined to be implemented or performed in an apparatus. Further, technical features in method claim(s) and apparatus claim(s) can be combined to be implemented or performed in a method. Other implementations are within the scope of the following claims. 

1. A method performed by a Central Unit (CU)-Control Plane (CP) of a Radio Access Network (RAN) node in a wireless communication system, the method comprising, establishing a connection with a wireless device for a Multicast and/or Broadcast Service (MBS); providing, via a CU-User Plane (UP) of the RAN node, the MBS by using a first transmission to the wireless device; receiving, from the CU-UP, a first message including a retransmission information on data transmission related to the MBS; determining whether to perform a switch of the first transmission to a second transmission for the MBS based on the retransmission information; and providing, via the CU-UP, the MBS by using the second transmission to the wireless device, wherein the first transmission is one of unicast transmission or multicast transmission, and the second transmission is another one of unicast transmission or multicast transmission.
 2. The method of claim 1, wherein the first message includes an identity (ID) of the MBS.
 3. The method of claim 1, wherein the retransmission information includes a retransmission rate per wireless device receiving the MBS.
 4. The method of claim 1, wherein the retransmission information includes a retransmission rate per bearer for the MBS.
 5. The method of claim 1, wherein the retransmission information includes a retransmission rate per MBS.
 6. The method of claim 1, wherein the first message is transmitted from the CU-UP periodically.
 7. The method of claim 1, wherein the first message is transmitted from the CU-UP based on that a certain condition is met.
 8. The method of claim 1, wherein the method further comprises, transmitting, to the CU-UP, a second message to request the switch of the first transmission to the second transmission for the MBS.
 9. The method of claim 8, wherein the second message includes an ID of the MBS and/or an ID of the wireless device.
 10. The method of claim 8, wherein the second message includes (1) multicast radio bearer (MRB) setup list including at least one MRB ID for the MBS, (2) Service Data Adaptation Protocol (SDAP) configuration for the MBS, (3) Packet Data Convergence Protocol (PDCP) configurations for the MBS, and/or (4) Quality of service (QoS) flow for the MBS.
 11. The method of claim 1, wherein the method further comprises, receiving, from the CU-UP, a third message informing establishment of radio resources for the MBS.
 12. The method of claim 11, wherein the third message includes (1) an ID of the MBS and/or (2) an MRB Setup List to inform established MRB resources for the MBS.
 13. The method of claim 1, wherein the method further comprises, transmitting, to a Distributed Unit (DU) of the RAN node, a fourth message to request the switch of the first transmission to the second transmission for the MBS, wherein the fourth message includes an ID of the MBS.
 14. The method of claim 13, wherein the method further comprises, receiving, from the DU, a fifth message informing that allocating radio resource for the second transmission is available, wherein the fifth message includes (1) channel information for the MBS, (2) the ID of the MBS, and/or (3) a downlink tunnel endpoint ID (DL TEID) for the MBS from the CU-UP to the DU.
 15. The method of claim 14, wherein the method further comprises, transmitting, to the CU-UP, a sixth message including (1) the ID of the MBS, and/or (2) the DL TEID.
 16. A Central Unit (CU)-Control Plane (CP) of a Radio Access Network (RAN) node in a wireless communication system comprising: a memory; and at least one processor operatively coupled to the memory, and configured to: establish a connection with a wireless device for a Multicast and/or Broadcast Service (MBS); provide, via a CU-User Plane (UP) of the RAN node, the MBS by using a first transmission to the wireless device; receive, from the CU-UP, a first message including a retransmission information on data transmission related to the MBS; determine whether to perform a switch of the first transmission to a second transmission for the MBS based on the retransmission information; and provide, via the CU-UP, the MBS by using the second transmission to the wireless device, wherein the first transmission is one of unicast transmission or multicast transmission, and the second transmission is another one of unicast transmission or multicast transmission.
 17. The CU-CP of the RAN node of claim 16, wherein the first message includes an identity (ID) of the MBS.
 18. The CU-CP of the RAN node of claim 16, wherein the retransmission information includes a retransmission rate per wireless device receiving the MBS.
 19. The CU-CP of the RAN node of claim 16, wherein the retransmission information includes a retransmission rate per bearer for the MBS. 20-31. (canceled)
 32. A non-transitory computer-readable medium having stored thereon a plurality of instructions, which, when executed by a processor of a Central Unit (CU)-Control Plane (CP) of a Radio Access Network (RAN) node in a wireless communication system, cause the CU-CP of the RAN node to: establish a connection with a wireless device for a Multicast and/or Broadcast Service (MBS); provide, via a CU-User Plane (UP) of the RAN node, the MBS by using a first transmission to the wireless device; receive, from the CU-UP, a first message including a retransmission information on data transmission related to the MBS; determine whether to perform a switch of the first transmission to a second transmission for the MBS based on the retransmission information; and provide, via the CU-UP, the MBS by using the second transmission to the wireless device, wherein the first transmission is one of unicast transmission or multicast transmission, and the second transmission is another one of unicast transmission or multicast transmission. 